CBL-5191 : Implement the partial index API (#596)

* Implement the partial index API and tests.

* Ensure to include null-terminated char when converting from FLString to const char* when using LiteCore C4 Index API (CBL-6669).

* Update LiteCore to 3.2.2-3.

include/cbl/CBLQueryIndexTypes.h

@@ -30,21 +30,28 @@ CBL_CAPI_BEGIN
 
 /** Value Index Configuration. */
 typedef struct {
-    /** The language used in the expressions. */
+    /** The language used in the expressions (Required). */
     CBLQueryLanguage expressionLanguage;
 
-    /** The expressions describing each coloumn of the index. The expressions could be specified
-        in a JSON Array or in N1QL syntax using comma delimiter. */
+    /** The expressions describing each coloumn of the index (Required).
+        The expressions could be specified in a JSON Array or in N1QL syntax
+        using comma delimiter, depending on expressionLanguage. */
     FLString expressions;
+
+    /** A predicate expression defining conditions for indexing documents.
+        Only documents satisfying the predicate are included, enabling partial indexes.
+        The expression can be JSON or N1QL/SQL++ syntax, depending on expressionLanguage. */
+    FLString where;
 } CBLValueIndexConfiguration;
 
 /** Full-Text Index Configuration. */
 typedef struct {
     /** The language used in the expressions (Required). */
     CBLQueryLanguage expressionLanguage;
 
-    /** The expressions describing each coloumn of the index. The expressions could be specified
-        in a JSON Array or in N1QL syntax using comma delimiter. (Required) */
+    /** The expressions describing each coloumn of the index (Required).
+        The expressions could be specified in a JSON Array or in N1QL syntax
+        using comma delimiter, depending on expressionLanguage. */
     FLString expressions;
 
     /** Should diacritical marks (accents) be ignored?
@@ -64,6 +71,11 @@ typedef struct {
         If left null,  or set to an unrecognized language, no language-specific behaviors
         such as stemming and stop-word removal occur. */
     FLString language;
+
+    /** A predicate expression defining conditions for indexing documents.
+        Only documents satisfying the predicate are included, enabling partial indexes.
+        The expression can be JSON or N1QL/SQL++ syntax, depending on expressionLanguage. */
+    FLString where;
 } CBLFullTextIndexConfiguration;
 
 /** Array Index Configuration for indexing property values within arrays
@@ -80,8 +92,9 @@ typedef struct {
 
     /** Optional expressions representing the values within the array to be
         indexed. The expressions could be specified in a JSON Array or in N1QL syntax
-        using comma delimiter. If the array specified by the path contains scalar values,
-        the expressions should be left unset or set to null. */
+        using comma delimiter, depending on expressionLanguage.
+        If the array specified by the path contains scalar values, the expressions
+        should be left unset or set to null. */
     FLString expressions;
 } CBLArrayIndexConfiguration;
 

src/CBLCollection_Internal.hh

@@ -111,20 +111,34 @@ public:
 #pragma mark - INDEXES:
 
     void createValueIndex(slice name, CBLValueIndexConfiguration config) {
-        C4IndexOptions options = {};
+        C4IndexOptions options {};
+
+        alloc_slice whereAlloc;
+        if (config.where.buf) {
+            whereAlloc = alloc_slice::nullPaddedString(slice(config.where));
+            options.where = (const char*)whereAlloc.buf;
+        }
+
         _c4col.useLocked()->createIndex(name, config.expressions,
                                         (C4QueryLanguage)config.expressionLanguage,
                                         kC4ValueIndex, &options);
     }
 
     void createFullTextIndex(slice name, CBLFullTextIndexConfiguration config) {
-        C4IndexOptions options = {};
+        C4IndexOptions options {};
+
         options.ignoreDiacritics = config.ignoreAccents;
 
-        std::string languageStr;
+        alloc_slice langAlloc;
         if (config.language.buf) {
-            languageStr = std::string(config.language);
-            options.language = languageStr.c_str();
+            langAlloc = alloc_slice::nullPaddedString(slice(config.language));
+            options.language = (const char*)langAlloc.buf;
+        }
+
+        alloc_slice whereAlloc;
+        if (config.where.buf) {
+            whereAlloc = alloc_slice::nullPaddedString(slice(config.where));
+            options.where = (const char*)whereAlloc.buf;
         }
 
         _c4col.useLocked()->createIndex(name, config.expressions,
@@ -133,8 +147,10 @@ public:
     }
 
     void createArrayIndex(slice name, CBLArrayIndexConfiguration config) {
-        C4IndexOptions options = {};
-        options.unnestPath = (char*)config.path.buf;
+        C4IndexOptions options {};
+
+        alloc_slice pathAlloc = alloc_slice::nullPaddedString(slice(config.path));
+        options.unnestPath = (const char*)pathAlloc.buf;
 
         auto exprs = config.expressions;
         if (!exprs.buf && config.expressionLanguage == kCBLJSONLanguage) {

test/QueryTest.cc

@@ -1287,6 +1287,88 @@ TEST_CASE_METHOD(QueryTest, "TestCreateArrayIndexWithPathAndExpressions", "[Quer
     CBLCollection_Release(collection);
 }
 
+#pragma mark - Partial Index
+
+// Spec: https://github.com/couchbaselabs/couchbase-lite-api/blob/master/spec/tests/T0007-Partial-Index.md
+// Version: 1.0.2
+
+TEST_CASE_METHOD(QueryTest, "TestCreatePartialValueIndex", "[Query]") {
+    CBLValueIndexConfiguration config {};
+
+    SECTION("SQL++") {
+        config.expressionLanguage = kCBLN1QLLanguage;
+        config.expressions = "num"_sl;
+        config.where = "type = 'number'"_sl;
+    }
+
+    SECTION("JSON") {
+        config.expressionLanguage = kCBLJSONLanguage;
+        config.expressions = R"([[".num"]])"_sl;
+        config.where = R"(["=",[".type"],"number"])"_sl;
+    }
+
+    CBLError error {};
+    CHECK(CBLCollection_CreateValueIndex(defaultCollection, "num-index"_sl, config, &error));
+    CheckNoError(error);
+
+    string queryString = "SELECT * FROM _ WHERE type = 'number' AND number > 1000";
+    query = CBLDatabase_CreateQuery(db, kCBLN1QLLanguage, slice(queryString), nullptr, &error);
+    REQUIRE(query);
+
+    alloc_slice exp = CBLQuery_Explain(query);
+    CHECK(exp.find("USING INDEX num-index"_sl));
+
+    CBLQuery_Release(query);
+
+    queryString = "SELECT * FROM _ WHERE type = 'foo' AND number > 1000";
+    query = CBLDatabase_CreateQuery(db, kCBLN1QLLanguage, slice(queryString), nullptr, &error);
+    REQUIRE(query);
+
+    exp = CBLQuery_Explain(query);
+    CHECK(!exp.find("USING INDEX num-index"_sl));
+}
+
+TEST_CASE_METHOD(QueryTest, "TestCreatePartialFullTextIndex", "[Query]") {
+    createDocWithJSON(defaultCollection, "doc1", "{\"content\": \"Couchbase Lite is a database.\"}");
+    createDocWithJSON(defaultCollection, "doc2", "{\"content\": \"Couchbase Lite is a NoSQL syncable database.\"}");
+
+    CBLFullTextIndexConfiguration config {};
+
+    SECTION("SQL++") {
+        config.expressionLanguage = kCBLN1QLLanguage;
+        config.expressions = "content"_sl;
+        config.where = "length(content) > 30"_sl;
+    }
+
+    SECTION("JSON") {
+        config.expressionLanguage = kCBLJSONLanguage;
+        config.expressions = R"([[".content"]])"_sl;
+        config.where = R"-([">", ["length()", [".content"]], 30])-"_sl;
+    }
+
+    CBLError error {};
+    CHECK(CBLCollection_CreateFullTextIndex(defaultCollection, "contentIndex"_sl, config, &error));
+    CheckNoError(error);
+
+    string queryString = "SELECT content FROM _ WHERE match(contentIndex, 'database')";
+    query = CBLDatabase_CreateQuery(db, kCBLN1QLLanguage, slice(queryString), nullptr, &error);
+    REQUIRE(query);
+    CheckNoError(error);
+
+    results = CBLQuery_Execute(query, &error);
+    REQUIRE(results);
+
+    int n = 0;
+    while (CBLResultSet_Next(results))
+    {
+        FLDict result = CBLResultSet_ResultDict(results);
+        slice content = FLValue_AsString(FLDict_Get(result, "content"_sl));
+        CHECK(content == "Couchbase Lite is a NoSQL syncable database.");
+        ++n;
+    }
+    CHECK(n == 1);
+}
+
 #ifdef COUCHBASE_ENTERPRISE
 
 TEST_CASE_METHOD(QueryTest, "Query Encryptable", "[Query]") {